Glutamate Receptors in Plants

Abstract
Ionotropic glutamate receptors function in animals as glutamate‐gated non‐selective cation channels. Numerous glutamate receptor‐like (GLR) genes have been identified in plant genomes, and plant GLRs are predicted, on the basis of sequence homology, to retain ligand‐binding and ion channel activity. Non‐selective cation channels are ubiquitous in plant membranes and may function in nutrient uptake, signalling and intra‐plant transport. However, there is little evidence for amino acid gating of plant ion channels. Recent evidence suggests that plant GLRs do encode non‐selective cation channels, but that these channels are not gated by amino acids. The functional properties of these proteins and their roles in plant physiology remain a mystery. The problems surrounding characterization and assignation of function to plant GLRs are discussed in this Botanical Briefing, and potential roles for GLR proteins as non‐selective cation channels involved in metabolic signalling are described.